[ale] RH9/General modules setup question

[James P. Kinney III]

On Tue, 2004-05-04 at 18:29, tfreeman at intel.digichem.net wrote:
> I don't think I'm asking the right question here, so bear with me please. 
> If I can get the question(s) (could be more than one I guess) straight, I 
> should have better luck searching out the answer in various doc sets.
> 
> Background. I purchased a Haupphauge TV/Radio card a few weeks ago, and 
> have it running with the application xawtv. Well, I also have a usb web 
> cam or three lying around, so I started plugging them in. And in a  
> fashion, I  have both the web cam and the TV capture board coexisting, and 
> expect to be able to add another web cam just for the excess of it. Sort 
> of.
> 
> The rub comes after a reboot. If I boot the system, access the TV card, 
> and then plug in the first web cam everything cooperates nicely. However, 
> reboot the system and just plug in the usb web cam can lead to trouble, as 
> the 
> web cam grabs /dev/video0, which the TV card expects to get. I have 
> managed (some how) to get both the web cam and the TV card to fight and 
> slow the system down to a crawl once, although I don't know exactly _how_ 
> I did that and haven't been able to recreate it.
> 
> What I want to do is specify that the TV card will attach and service 
> /dev/video0, while the web cam(s) line up with /dev/video[12345]. My 
> /etc/modules.conf file has the line "alias char-major-81 bttv" already, on 
> the advice of the bttv-HOWTO, which allows the bttv module & others to 
> dynamically load when starting xawtv.
> 
> In addition to having the video devices line up _my_ way, I'd like to 
> understand how the kernel attaches a device module to a /dev/* entry. 
> Additionally, how useful is the alias command (example above) to setting 
> up a module to manage a specific device?
> 
> Hopefully this has all made sense to somebody. Your help and listening is 
> appreciated.
> 
> FWIW - I gather that this sort of challenge is part of what the (?) devfs 
> file system is supposed to address.

That is exactly why the devfs stuf is important!

What you need to look into is the hotplug stuff. This will allow
USB/Firewire devices to be attached to the same /dev device when they
get plugged in. It uses the USB device ID numbers so that two different
brands of web cam's will show up on two different places no matter the
plug-in order.
-- 
James P. Kinney III          \Changing the mobile computing world/
CEO & Director of Engineering \          one Linux user         /
Local Net Solutions,LLC        \           at a time.          /
770-493-8244                    \.___________________________./
http://www.localnetsolutions.com

GPG ID: 829C6CA7 James P. Kinney III (M.S. Physics)
<jkinney at localnetsolutions.com>
Fingerprint = 3C9E 6366 54FC A3FE BA4D 0659 6190 ADC3 829C 6CA7
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